The present invention relates to a vehicle wiper device.
Japanese Laid-Open Patent Publication No. 4-197854 describes a vehicle wiper device provided with drivers, each including a drive source and a link mechanism. The drivers are arranged in the vehicle below the two lateral sides of the windshield. Each drive source includes a motor body and a reduction drive. Each link mechanism includes a wiper joint coupled to a wiper. The wipers are arranged to overlap each other in a wiping direction at their bottom reversing positions (stop positions). The above publication discloses a technique that increases the accuracy for controlling the position of a worm wheel in each reduction drive, which forms part of the corresponding drive source, to prevent interference between the driver side wiper and the passenger side wiper.
In the vehicle wiper device, the link mechanism reduces the speed to increase torque of the corresponding wiper when the wiper is performing a wiping operation. This allows for a decrease in the torque generated by the drive source and thus allows for the drive source to be reduced in size. However, the torque of the wiper during a wiping operation differs in accordance with the wiping angle of the wiper. Referring to FIG. 5 that shows curve X1 in broken lines, the link mechanism is usually formed to significantly increase the torque in the proximities of the stop position and a top reversing position in a symmetrical manner relative to the center of the wiping angle. This increases the torque and reduces the speed in the vicinity of the stop position (0°) thereby improving the stop position accuracy, that is, the accuracy of the control for stopping the wiper at the stop position. However, in the vehicle wiper device, the wiper speed lowered in the proximity of the top reversing position (approximately 90°) prolongs the time in which the wiper remains in the proximity of the top reversing position. This blocks the field of view of the vehicle occupant for a longer time.
The drivers of the vehicle wiper device described above are arranged proximal to the lateral ends of the vehicle. Thus, the drivers may interfere with the vehicle body or the like. To prevent such interference, the drivers may be arranged at inwardly locations in the lateral direction of the vehicle. However, when the pivot center of the wiper is located inwardly in the lateral direction of the vehicle, the wiper would be significantly inclined outwardly in the lateral direction relative to the front pillar at the top reversing position. This would form a large non-wiped area.